Mucin-hypersecreting biliary neoplasm excretes excessive mucin that fills the biliary tree and results inmarked dilatation of the bile ducts and obstructive jaundice. In these neoplasm, the mucin produced by the tumorrather than the tumor itself plays an important role in clinical course and radiologic patterns. The purpose ofthis paper is to report characteristic radiologic patterns of mucin-hypersecreting biliary neoplasms in two cases.These neoplasms were characterized by not only multilocular cystic hepatic mass or extra-hepatic bile duct massresulting in marked biliary dilatation distal to the mass on US or CT, but also change of shape and extent ofamorphous filling defects in the markedly dilated bile duct on serial cholangiograms.